After an interminably long wait, the government is set to publish its review of climate change policies today. At last, warring government departments have had their heads banged together and been told to get on with reducing Britain's greenhouse gas emissions.

That's the hope, at least. But the expectation-management gurus have already been hard at work ensuring that ministers have been giving out the signal that the review will not be as comprehensive as environmental campaigners might wish. Expect, therefore, the usual stock phrases about "having to achieve realistic goals without damaging economic growth" and how "we must manage change that benefits all partners". It's a foolish bookie these days who offers attractive odds on Long-Term Thinking defeating Short-Term Thinking.

The government's problems in this realm reflects our own in many ways. Neither are we too keen to go down a path that impinges on our lifestyle choices or costs us more - especially when it's for what some still see as a nebulous, far-off gain. That's largely why carbon-offset schemes have proved popular with people, and businesses, wanting to "do their bit". Calculate how much carbon dioxide pollution your action - flying to Florida, heating your home, driving to work - is responsible for, and then pay a modest fee to a company to "offset" these emissions through various schemes such as tree planting, building renewable energy infrastructure or dispersing energy-efficient light bulbs in various developing nations. In its ideal, it's a cuddly and voluntary form of punitive taxation.

But since these schemes started in the 1990s they have had their critics, most notably from those who question the science of "forestry sequestration" - the act of planting trees to "soak up" the carbon dioxide we pump into the atmosphere. "What "offset" forestry does is confuse fossil carbon with biological carbon," says Fern, the campaign group that lobbies against policies or actions that "impact on forests and forest peoples' rights globally". It is erroneous to believe, the group says, that the planting of a tree neutralises any CO2 released from the "fossil carbon pool". It cites Oliver Rackham, a botanist and landscape historian at Cambridge University, who says: "Telling people to plant trees is like telling them to drink more water to keep down rising sea levels." Fern also says that if you took the claims at face value then you would need to plant a forest the size of Devon and Cornwall every year to soak up Britain's annual greenhouse gas emissions.

Worse, perhaps, is the wider message these schemes send out, says Fern. "Carbon offset projects may salve our conscience but they won't solve the problem of global warming. On the contrary, by creating the illusion that 'all is well', as long as we pay a little extra, they may further delay global agreement on decisive action to avert dangerous climate change."

The carbon offset firms have been quick to react to any potential backlash caused by such doubters. Future Forests, perhaps the most high-profile firm with its celebrity endorsements, changed its name last year to the CarbonNeutral Company, recognising that its former name linked it too closely with tree-planting schemes and has now moved beyond what some critics saw as its no-worries-just-plant-some-trees position. While it still vigorously defends forestry sequestration, believing that "in the UK a forest typically offsets 70 tonnes of carbon per hectare", it has widened its services, principally for businesses, to include "emissions assessments, advice on reductions, offset and communication."

"There are 'purists' who believe that the only way to address climate change is to reduce emissions," the company says. "We agree that reductions are critical to dealing with the issue. However, our view is that reductions and offset are all part of the approach we should be taking. The fact is that until new technologies are commercialised, people will continue to drive cars, take flights and use energy from fossil fuel sources. Once a client has reduced CO2 emissions as far as possible, 'offset' is the only way to deal with the unavoidable emissions. By helping people to take this first simple step, individuals can be switched on to reducing their emissions through improving energy efficiency at home, switching to renewables, etc."

While it could be argued that there's no harm in supporting a scheme that plants more trees or builds wind turbines, the "purists" are right: there is no substitute for reducing emissions and inaction could be a byproduct of the notion, however well meaning, that there is somehow an alternative

You say ...

Carbon offsets are one of the most scientifically and environmentally dubious industries emerging today. They merely provide moral cover for western middle-class consumers, governments and corporations for their profligate use of fossil fuels. No amount of carbon chicanery is going to adequately deal with the problemand it only delays more effective action while muddying the debate. Stop this insanity now.Adam Ma'anit, New Internationalist

If we are to make the really deep cuts in emissions that are necessary, then we will all need personal carbon allowances and carbon will have to be priced into everything we do. Carbon offsets are a first step towards pricing carbon in our daily lives - as well as making real emissions reductions in the process.Tom Morton, Climate Care